Color stabilization of fatty-acid forerunnings



United States Patent "ice 3,531,506 COLOR STABILIZATION OF FATTY-ACIDFORERUNNINGS Sasauka Sekhar Naskar, Witten (Ruhr), Hans Leo Hiilsmann,Wengern, and Gustav Renckhotf, Witteu (Ruhr), Germany, assignors toDynamit Nobel Aktiengesellschaft, Witten (Ruhr), Germany N0 Drawing.Filed June 25, 1969, Ser. No. 836,624 Claims priority, applicationGzrmany, June 26, 1968,

Int. cl. Cllc 1/10 US. Cl. 260419 11 Claims ABSTRACT OF THE DISCLOSUREDiscoloration and subsequent darkening of fatty-acid forerunnings areprevented by heating the fatty acids with at least one alkyl ester ofsilicic acid, polysilicic acid and/or carbonic acid at a temperature ofapproximately 180-250 C., and then distilling the resultant mixture torecover the fatty acids. The heating step is carried out for about 0.5-8hours.

BACKGROUND OF THE INVENTION The state of the art can be seen from aconsideration of US. Pat. 2,862,943 and from German DAS 1,214,212.Inorganic and organic compounds have been conventionally employed in theart for preventing discoloration. However, as discussed in said Germanpublication, these conventional processes have many disadvantages. Whenusing the organic and inorganic compounds of boric acid, unsaponifiablecondensation products of the fatty acids are obtained in thedistillation residue. In fact, the production of exactly thesecondensation products from fatty acids is described in DAS 1,073,665,wherein oxygencontaining boron compounds are employed as condensationcatalysts. The yield of unsaponifiable condensation products, inaccordance with this process, is up to 92%. US. Pat. 2,583,028 andBritish Pat. 1,081,522 describe the treatment of fatty acids with borontrifiuoride or with the ether complex thereof. However, extremely gravecorrosion problems are encountered in these processes.

One of the objects of the present invention is to provide a process forpreventing the discoloration and subsequent darkening of fatty-acidforerunnings.

Another object of the present invention is to provide a novel processfor purifying fatty acids and for preventing the formation ofunsaponifiable compounds therein which overcomes the disadvantages anddeficiencies of the prior art methods.

A further object of the invention is to provide fatty acids of improvedcolor, even when using low grade substances as starting materials.

These and other objects and advantages of the present invention willbecome apparent to those skilled in the art from a consideration of thefollowing specification and claims.

SUMMARY OF THE INVENTION In accordance with the present invention, ithas been 3,531,506 Patented Sept. 29, 1970 found that the discolorationand subsequent darkening of the first-or forerunnings of fatty acidshaving 8-12 carbon atoms can be prevented by heating the fatty acidswith about 0.2-2% by weight, preferably 0.5-1% by weight, based on theamount of fatty acid employed, of an alkyl ester of silicic acid,polysilicic acid, carbonic acid or mixtures thereof. Heating isconducted for approximately 0.5-8 hours, preferably 2-4 hours, totemperatures of about ISO-250 0., preferably to ZOO-240 C., under normalpressure. Slight superatmospheric pressures of up to about 5 atmospheresgauge can be optionally used when a low-boiling alkyl ester of silicicacid and/or carbonic acid is employed. Thereafter, the fatty acids aredistilled.

The fatty-acid forerunnings treated in accordance with the presentinvention are obtained as the first runnings or heads during thedistillation of fatty acids from the hydrolysis of coconut oil or palmnut oil. The neutralization of the free fatty acids in crude coconut oiland palm nut oil with alkali results in the formation of soap. Theseparated soap solution is known as soap stock, which contains someneutral oil. It is hydrolyzed or split by acidulation with mineral acidswhich causes a separation of the fatty acids along with the neutral oil.This mixture of fatty matters is known as acid oil. This acid oil ishydrolyzed, and the fatty acids obtained by distillation have aninferior color quality as compared with fatty acids obtained by thedirect hydrolysis of coconut or palm nut oil. Also, a distinction shouldbe made between the fatty acids from hydrolyzed acid oil obtained bysplitting of soap stock during the refining of coconut oil or palm nutoil, and fatty acids from the pressure-hydrolysis of coconut oil or palmnut oil. The fatty acids from hydrolyzed acid oil obtained by splittingof soap stock exhibit a poorer color quality than the fatty acidsobtained by direct hydrolysis of coconut oil or palm nut oil and tend toexhibit discoloration and subsequent darkening to an even greater extentthan the latter. The process of the present invention, however, makes itpossible to also produce color-stable distillates from the fatty acidsfrom hydrolyzed acid oil obtained by splitting of soap stock during therefining of coconut oil and palm nut oil.

In Examples 1 to 4, set out below, fatty-acid forerunnings of arelatively low quality were employed, stemming from fatty acids'fromhydrolyzed acid oil. A comparison with Examples 5 and 6 makes it clearthat the color stability of fatty-acid forerunnings obtained from thehydrolysis of coconut oil or palm nut oil under pressure is considerablyhigher.

The color stability of the fatty-acid forerunnings treated in accordancewith the invention as well as that of the untreated materials wasdetermined by heating the samples in a small glass tube having adiameter of 14 millimeters and a filling height of 115 millimeters to200 C. during a period of 6 hours. This heating test was conducted in athermostatically controlled oven which was not opened during the entireduration of the test. The test tubes were each covered with a cap.

The color intensity was measured in iodine color number units, whereinthe iodine color number indicates how many milligrams of free iodine arecontained in milliliters of aqueous iodine-potassium iodide solution atthe same depth of color, when measured at a layer thickness of 25millimeters.

The process according to the present invention can be conductedbatch-wise as well as continuously.

The following examples are given merely as illustrative of the presentinvention and are not to be considered as limiting. Unless otherwisenoted, the percentages therein and throughout the application are byweight.

3 EXAMPLES THE INVENTION Example 1 The untreated fatty-acid forerunningsemployed had the following composition, according to gas chromatographicanalysis (numerical data in percent by weight): C -acid: 0.2; C -acid:68.4; C -acid: 23.5; C -acid: 7; C -acid: 0.5; C -acid: 0.2; methylheptyl ketone: 0.2 and methyl nonyl ketone: 0.2.

2,400 parts by weight of the above described fatty-acid forerunnings,containing approximately 2% of water, were dehydrated with agitation andmixed, at a sump temperature of 240 C., with 0.5% by weight of silicicacid tetrabutyl ester or the dibutyl ester of carbonic acid. Thetreatment time was 3 hours. During this time, a temperature of 240 C.was maintained. Thereafter, the sump temperature was lowered to 100 C.by cooling, and the contents of the flask distilled over a smalldistillation column under a vacuum of 3-5 torr [mm. Hg] within about 2hours, 3 fractions being withdrawn, For comparison purposes, 2,400 partsby weight of untreated fattyacid forerunnings were distilled under thesame conditions (Example 1a).

As fraction 1, 55-10% by weight was obtained; as fraction 2, 76-78% byweight; as fraction 3, 57% by weight, based on the initial charge ofanhydrous fatty-acid forerunnings. The amount of residue was 79% byweight.

The values are compiled in Table I.

Example 2 The procedure of Example 1 was repeated with the exception ofthe treatment time, amounting to 8 hours, all of the other conditionsbeing identical to those set forth in Example 1. Table I shows themeasured values which were obtained.

Example 3 2,400 parts by weight of the above fatty-acid forerunningswere dehydrated, and 1% by weight of the ethyl 4 ester of polysilicicacid was added thereto at2007 C LThe charge was maintained at 200 C. for6 hours and then distilled under a vacuum. Three fractions wereobtained. The data resulting from this experiment are listed in TableII.

Example 4 Five tons of the above fatty-acid forerunnings were dehydratedat 450 torr. At 220 C., 0.7% by weight of the tetrabutyl ester ofsilicic acid was added, and the temperature of the charge was maintainedat 220-240" C. for 3 hours. Thereupon, the charge was cooled to C. andfractionally distilled in a continuous distillation plant under a vacuumof 5 torr. The characteristic data of the thus-obtained three fractionsare set forth in Table II.

Example 5 (a) 2,400 parts by weight of fatty-weight forerunnings fromthe hydrolysis of coconut oil were dehydrated, and 0.5 by weight of theethyl ester of polysilicic acid was added thereto at 240 C. The chargewas maintained at 240 C. for 3 hours and thereafter distilled under avacuum. The characteristic data of the three fractions and the residuecan be seen from Table III.

(b) For comparison purposes, 2,400 parts by weight of untreated fattyacids from a coconut oil hydrolysis were distilled under the sameconditions as set forth in (a), in three fractions, the resulting dataalso being shown in Table III.

Example 6 2,400 parts by weight of fatty-acid forerunnings derived fromthe hydrolysis of coconut oil and palm nut oil were dehydrated and thenmixed with 0.8% by weight of the ethylbutyl ester of carbonic acid at C.Within 6 hours, the temperature was increased to 240 C., and the chargewas subsequently distilled under a vacuum. The characteristic values ofthe three fractions and the residue are indicated in Table III.

TABLE I Fraction I C llodiIne 0 or 0. Duration of Amount after 6 4treatment; (percent Iodine hours at Example Additive (hours) by wt.)Acid No. color N 0. 200 C.

1(a) Without additive 0 8. 8 380 5. 2 104 1(b). 0.5% by weight of thetetrabutyl ester of oi'tho- 3 9. 0 378 1. 0 38 si icic aci 1(c). 0.5%dbyweight of the dibutyl ester of carbonic 3 9. 8 377 1. 5 48 am 2(a) 0.5%by weight of the teti-abutyl ester of ortlio- 8 8. 6 381 1 33 silicicacid. 2(1)) 0.5%oy weight of the dibutyl ester of carbonic 8 8. 1 379 1.3 42 Fraction II Fraction III Residue C 1Iorilne Iodinc 0 or 0. ColorNo. Content of Amount Iodine after 6 Amount Iodine after 6 Amountunsaponifiable (percent Acid Color hours at (percent Acid Color hours at(percent compounds Example by Wt.) No. No 200 C. by wt.) No. No 200 C.by wt.) (percent by wt.)

TABLE II Content of Iodine unsapon- Color N 0.. ifiable com- AmountIodine after 6 pounds (percent Color hours at (percent Fraction by wt.)Acid No. No 200 C by w Example 3 1 7.8 381 1 18.0 0.8 2 79. 5 375 1 6.20. 6 5. 5 312 2. 2 15. 3 1. 0 7. 2 252 3. 6 Example 4 1 6 384 1. 2 530.9 2 78 376 1 7. 8 0. 6 12 320 2. 1 18. 2 0. 5 Residue 4 6. 6

TABLE III Content of Iodine unsapon- Color No. ifiable com- AmountIodine after 6 pounds (percent Color hours at (percent Fraction by wt.)Acid No. No 200 C. by wt.)

Example (a). l 5. 2 360 1 12 0. 6 2. 83. 2 353 1 4. 2 0.3 6. 4 256 1. 2l4 0. 4 R 5. 2 242 1. 5 Example 5(b) 5.0 359 2. 2 60 0.6 83. 4 352 1.835 0. 3 6. 8 254 l 0 0. 4 4. 8 241 l. 6 Example 6 1. 5. 3 340 1 15 0. 72. 83. 0 335 l 3.8 0. 2 3. 6. 6 242 1. 3 l3 0. 2 Residue 5. 1 230 1. 8

The alkyl esters shown in the examples are merely exemplary of theadditives which may be employed in accordance with the invention.Generally, the alkyl groups in said alkyl esters have from 1 to 4 carbonatoms (usually designated as lower alkyl) and include groups such asmethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl andtert-butyl.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included herein.

We claim:

1. A process for preventing the discoloration and subsequent darkeningof fatty-acid forerunnings having from 8 to 12 carbon atoms whichcomprises heating the fatty acids with at least one alkyl ester of anacid selected from the group consisting of silicic acid, polysilicicacid and carbonic acid at a temperature of approximately 180- 250 C.,and then distilling the resultant mixture to recover the fatty acids.

2. The process of claim 1, wherein 0.22% by weight of said alkyl esterof silicic acid, polysilicic acid or carbonic acid or a mixture thereofis added to said fatty-acid forerunnings.

3. The process of claim 1, wherein the alkyl ester additive is heatedwith said fatty-acid forerunnings for about 0.5-8 hours.

4. The process of claim 1, wherein a low-boiling alkyl ester of silicicacid or carbonic acid or a mixture thereof is heated with saidfatty-acid forerunnings under a slight superatmospheric pressure of upto about 5 atmospheres gauge.

5. A process for preventing the discoloration and subsequent darkeningof fatty-acid forerunnings having from 8 to 12 carbon atoms whichcomprises heating the fatty acids with about 0.2-2% by weight of analkyl ester of silicic acid, polysilicic acid or carbonic acid or amixture thereof for approximately 0.5-8 hours at a temperature of about-250 0., and then distilling the resultant mixture to recover the fattyacids.

6. The process of claim 5, wherein 0.51% by weight of said alkyl esteris added to said fatty-acid forerunnings.

7. The process of claim 5, wherein heating is carried out for 2-4 hours.

8. The process of claim 5, wherein the mixture of fattyacid forerunningsand alkyl ester is heated at 200240 C.

9. The process of claim 5, wherein a low-boiling alkyl ester of silicicacid or carbonic acid or a mixture thereof is heated with saidfatty-acid forerunnings under a slight superatmospheric pressure of upto about 5 atmospheres gauge.

10. The process of claim 5, wherein said process is conductedcontinuously.

11. The process of claim 5, wherein the alkyl groups in said alkyl esterhave from 1 to 4 carbon atoms.

References Cited UNITED STATES PATENTS 3,052,701 9/1962 Hampton 2604l9LEWIS GOTTS, Primary Examiner E. G. LOVE, Assistant Examiner

